Analog television (TV) receivers often down-convert analog TV transmissions from a first radio frequency (RF) to an intermediate frequency (IF) signal in a component known as a tuner. The IF signal passes through two highly selective filters, one for video IF (VIF) and another for sound IF (SIF), typically constructed using surface acoustic wave (SAW) technology. The tuner provides the resulting video IF (VIF) signal to a video demodulator to recover the baseband video (composite video blanking and synchronization or CVBS) and its carrier. The carrier is typically recovered and applied to the sound IF (SIF) signal to further frequency-translate the SIF signal to a second IF frequency known as an inter-carrier SIF, a second (2nd) SIF or SSIF. A sound channel demodulator can then be applied to the SSIF signal to recover baseband audio signals. The tuner, being sensitive to radio frequency (RF) interference, is typically contained in a metalized can, which is designed to shield the tuner from RF interference, including interference generated by switching noise and other spurious RF interference. The analog TV demodulator and sound demodulator may or may not be co-located within the metalized can and may or may not be integrated with the tuner, depending on cost, performance, and system architecture considerations.
In conventional digital TV reception, a similar implementation exists. A tuner, the performance parameters of which are optimized differently for digital TV (DTV) transmissions than for analog TV (ATV), down-converts the DTV signals from an RF signal to an IF signal for filtering through a SAW filter with performance characteristics different than those required for ATV. The resulting IF signal is presented to a DTV demodulator, which decodes the IF signal to produce a digital output known as a Moving Picture Experts Group (MPEG) transport stream (TS). The tuner is typically enclosed in a metalized can to suppress RF interference, and the digital demodulator is typically placed outside of the metalized can due to the potential for the digital demodulator to contribute significantly to RF interference.